Some of the older hands around here may know better, but here's my understanding:
* Channel numbering in 5GHz is based on 5MHz-wide channels, just like in 2.4GHz. But no equipment uses less than 20MHz-wide channels, thus your choices are always 4 channel numbers apart. Partially-overlapping channels are not a thing here (thank goodness).
* 40MHz or wider channels are made by ganging adjacent channels. For example, if you choose channel 40 as your primary channel, your gear transmits in that channel until it has need for more than 20MHz bandwidth. When it does, it will combine the 36 and 40 channels to make a 40MHz channel. If it needs more than that, it adds channels 44 and 48 to make an 80MHz channel. If it needs more than that, it adds the next 4 channels to make a 160MHz channel.
* If your neighbor is, say, using channel 44 as primary channel, your signals don't interfere as long as both of you need up to 40MHz bandwidth (because his first step up is to 44+48). As soon as either of you need 80MHz, you are transmitting on the same frequencies and only one of you can broadcast at a time.
* I use these particular channel numbers because, depending on where you live, they might be the only ones you can use. There is a second set of 4 available WiFi channels at 149/153/157/161, but not every country allows their use.
* The channels between 48 and 149 are theoretically available to WiFi gear, but with a huge caveat: that is the "DFS range" of frequencies which WiFi gear is only allowed to use if it cannot hear anything else broadcasting on the frequency. In particular, a big chunk of that range is used by aviation radar and weather radar. If you live anywhere near an airport or weather radar station, your gear will see the radar pulses and drop off the channel, probably for minutes at a time. If your primary channel is in this range, what "drop off" means is you've got no WiFi at all. If your primary channel is one of the safe ones I listed above, and your gear is well designed, it will just back down to using at most an 80MHz channel (using the four adjacent safe channels).
* A lot of people have found that that back-off doesn't work so well, so they just set their gear to not use more than 80MHz channel width ever.
* So in short: if you don't have any near neighbors using 5GHz WiFi, just choose any one of the safe channels and be happy. Try letting your gear use 160MHz bandwidth, but if it seems unstable, one of the first things to try is restricting it to 80MHz so it stays out of the DFS range.
* If you do have near WiFi neighbors ("near" being within maybe 100 yards/meters), you want to try to not share channels with them. Most consumer gear has provisions for auto-selecting a lesser-used channel, but it's not unusual for that mode to make stupid choices. You might have to manually choose a channel. Best case is if you're on the low channels and your neighbor's on high or vice versa; then you both can use 80 or even 160 MHz without overlap. Otherwise, at least try not to be sharing the same 40MHz channel pair.